Description of study sample. In the 3 years combined, we surveyed a total of 99 villages: 46 in the Makueni district and 53 in the Kitui district. Within those villages, we surveyed 705 households. Most [676 (96%)] of these households were randomly selected, and the remaining 29 (4%) were systematically selected households with an aflatoxicosis case-patient (cases who had been hospitalized) who was identified by hospital-based clinical disease surveillance in 2005 (). Eleven of the 705 households had maize from two different sources; therefore, we collected a total of 716 maize samples. We collected most (42%) of the 716 samples in 2005, followed by 35% in 2007, and 23% in 2006.
Description of study sample by year.
Maize production. In 2005, most participants (96%) reported that their maize crop production was less than in previous years, and only 83 (28%) of the 298 maize samples collected were homegrown (grown on the household farm), whereas 215 (72%) were either purchased or obtained from the Kenyan government. In contrast, 97 (59%) of the maize samples collected in 2006 were homegrown. On average, households reported harvesting 328 kg (approximately four 90-kg bags) of maize in 2006. Maize production increased substantially in 2007 compared with the previous 2 years. All of the 256 samples collected in 2007 were homegrown, and none of the households reported purchasing maize or requesting relief maize. On average, households reported harvesting 1,169 kg (13 bags) of maize, or triple the harvest of 2006.
Aflatoxin contamination. For all 3 years combined (2005, 2006, and 2007), maize aflatoxin levels ranged from nondetectable to 48,000 ppb. The GM aflatoxin level for all 3 years combined was 9.10 ppb, and more than a third [248 (35%)] of the 716 maize samples had aflatoxin levels above the 20-ppb regulatory limit (). However, aflatoxin levels varied considerably by year, with GM levels decreasing dramatically in 2007 (GM = 1.95) compared with 2005 (GM = 12.92) and 2006 (GM = 26.03; p-value < 0.0001) ().
Summary of the extent of aflatoxin contamination among all households, 2005–2007.
We collected the maize sample with the highest aflatoxin level (48,000 ppb—2,400 times the regulatory limit for human consumption) in 2005, and the sample with the second highest level (24,400 ppb) in 2006. In the non-outbreak year (2007), contamination was much lower than in the previous 2 years; the two samples with the highest contamination had aflatoxin levels of 2,500 ppb and 470 ppb. In 2005 and 2006, 41% and 51% of samples, respectively, had aflatoxin levels above the 20-ppb regulatory limit compared with 16% of samples in 2007 (). In addition, 21 samples (7%), 14 samples (8%), and 1 sample (0.4%) had aflatoxin levels > 1,000 ppb in 2005, 2006, and 2007, respectively ().
Source of maize and aflatoxin contamination. We assessed and compared the extent of aflatoxin contamination in the three sources of maize in the region (homegrown, purchased, and relief) in 2005 and 2006 when all three sources of maize were collected from households and tested. In 2007, production was high, and all households had only homegrown maize. Most of the homegrown maize samples collected in 2005 and 2006 had aflatoxin levels above the 20-ppb regulatory limit (64% and 60%, respectively) compared with 41% and 40% of purchased maize samples (). Of the relief maize tested, three of 53 (6%) relief samples in 2005 and one of three (33%) in 2006 exceeded the 20-ppb limit. We found the highest levels of aflatoxin contamination in 2005 and 2006 (48,000 ppb and 24,400 ppb, respectively) in homegrown maize samples. Relief maize had considerably lower aflatoxin levels (see ). In 2005, the aflatoxin level of homegrown maize (GM = 62.61) was significantly higher than the level of purchased maize (GM = 10.05) or of relief maize (GM = 1.99) (p-value < 0.0001). We also found similar, statistically significant differences in levels among the different sources in 2006 (p-value < 0.0001) ().
Maize aflatoxin levels by source, 2005–2007.
Geometric mean aflatoxin levels in homegrown maize samples according to responses to aflatoxin awareness questions, 2005–2007.
When comparing aflatoxin levels in homegrown maize between years, the GM homegrown maize aflatoxin levels were significantly higher in 2005 (GM = 17.96) and 2006 (GM = 3.64) compared with 2007 (GM = 0.73) (p-value < 0.0001). We found no significant difference in homegrown maize aflatoxin levels in 2005 compared with 2006.
Aflatoxin contamination and jaundice. We asked questions about the health of family members residing in the household, specifically, if any household members had symptoms of jaundice. Of the 696 randomly selected households in all 3 years combined (not including the aflatoxicosis case households), 13 (2%) reported that one or more family members residing in the household had symptoms of jaundice at the time the survey was conducted. The GM aflatoxin levels in maize being consumed by households reporting jaundice ranged from 4.02 to 18.57 ppb. The maximum aflatoxin levels found among households with jaundice was 820 ppb. No jaundice was reported among households consuming maize with aflatoxin levels > 1,000 ppb, including those consuming the highest concentrations (48,000 ppb, 24,000 ppb).
Aflatoxin awareness. When assessing aflatoxin awareness, we limited our analysis to the 436 respondents who had homegrown maize at the time of sampling to determine a potential association between level of awareness and aflatoxin concentrations in their homegrown maize. For all 3 years combined, 59% of our study participants with homegrown maize reported receiving information about drying and storing maize. There was a statistically significant increase in the percentage of people who reported receiving information in 2007 [190/256 (74%)] compared with 2005 [31/82 (38%)] and 2006 [35/96 (36%)] (p-value < 0.0001) (). However, we found no significant difference in GM aflatoxin levels between households that reported receiving information and those that did not (overall or by year). Although the difference was not statistically significant, in 2006 the GM aflatoxin levels were considerably lower in households that reported receiving information ().
We asked respondents if they thought eating moldy maize could cause muuku (jaundice); 252 (75%) respondents in all 3 years combined responded “yes” to this question. We found a statistically significant difference in percentage of those who reported thinking that jaundice may be caused by eating moldy maize when comparing 2005 and 2006 (62% and 63%, respectively) with 2007 (82%) () (p-value < 0.0001). However, responses were not associated with statistically significant differences in GM aflatoxin levels ().
Finally, we asked respondents if they had heard about people getting muuku from eating moldy maize. In all 3 years combined, 216 (51%) of respondents answered yes to this question (). We found no statistically significant difference by year in proportions of those who responded yes to this question and no statistically significant differences in GM maize aflatoxin levels for those who responded yes compared with those who responded no.